utility-ht-0.0.17.2: Various small helper functions for Lists, Maybes, Tuples, Functions

Safe Haskell | Safe-Inferred
Language | Haskell98

Data.List.Match

Synopsis

- take :: [b] -> [a] -> [a]
- drop :: [b] -> [a] -> [a]
- splitAt :: [b] -> [a] -> ([a], [a])
- takeRev :: [b] -> [a] -> [a]
- dropRev :: [b] -> [a] -> [a]
- replicate :: [a] -> b -> [b]
- equalLength :: [a] -> [b] -> Bool
- compareLength :: [a] -> [b] -> Ordering
- lessOrEqualLength :: [a] -> [b] -> Bool
- shorterList :: [a] -> [a] -> [a]

# Documentation

take :: [b] -> [a] -> [a] Source #

Make a list as long as another one

    \(Shape xs) (List ys) -> Match.take xs ys == List.take (length xs) ys

drop :: [b] -> [a] -> [a] Source #

Drop as many elements as the first list is long

    \(Shape xs) (List ys) -> Match.drop xs ys == List.drop (length xs) ys

    \(Shape xs) (List ys) -> Match.take xs ys ++ Match.drop xs ys == ys

splitAt :: [b] -> [a] -> ([a], [a]) Source #

    \(Shape xs) (List ys) -> Match.splitAt xs ys == (Match.take xs ys, Match.drop xs ys)

    \(Shape xs) (List ys) -> Match.splitAt xs ys == List.splitAt (length xs) ys

takeRev :: [b] -> [a] -> [a] Source #

    \(Shape xs) (List ys) -> Match.takeRev xs ys == reverse (Match.take xs (reverse ys))

dropRev :: [b] -> [a] -> [a] Source #

    \(Shape xs) (List ys) -> Match.dropRev xs ys == reverse (Match.drop xs (reverse ys))

replicate :: [a] -> b -> [b] Source #

Specialisation of `$>`.

equalLength :: [a] -> [b] -> Bool Source #

Check whether two lists with different element types have equal length. It holds

    \(Shape xs) (List ys) -> equalLength xs ys == (length xs == length ys)

but `equalLength` is more efficient.

compareLength :: [a] -> [b] -> Ordering Source #

Compare the length of two lists over different types. It holds

    \(Shape xs) (List ys) -> compareLength xs ys == compare (length xs) (length ys)

but `compareLength` is more efficient.

lessOrEqualLength :: [a] -> [b] -> Bool Source #

`lessOrEqualLength x y` is almost the same as `compareLength x y <= EQ`, but

    >>> lessOrEqualLength "" undefined
    True

whereas `compareLength [] undefined <= EQ = undefined`.

shorterList :: [a] -> [a] -> [a] Source #

Returns the shorter one of two lists. It works also for infinite lists as much as possible. E.g.

    >>> shorterList (shorterList (repeat 'a') (repeat 'b')) "abc"
    "abc"

The trick is, that the skeleton of the resulting list is constructed using `zipWith` without touching the elements. The contents is then computed (only) if requested.